We are studying the functional characteristics of the central nervous thermoregulatory system of birds and mammals. Studies include measurements of hypothalamic thermosensitivity as a function of arousal state (wakefulness, slow wave sleep, or paradoxical sleep), torpor, circadian time, ambient temperature, and adaptive species differences. In birds we are studying the characteristics of spinal thermosensitivity as a function of arousal state and circadian time. Neurophysiological studies include extra cellular recordings of hypothalamic and mid brain reticular formation neurons during wakefulness, sleep, and torpor while manipulating hypothalamic and/or peripheral and/or spinal temperatures. We hope to obtain neurophysiological correlates of the integrative activities of this regulatory system as revealed by our other studies.